Insertable or implantable coated medical devices have been used to treat a variety of medical conditions. For example, stents coated with drugs allow for the localized delivery of drugs into the body lumen. Drug-eluting stents have been used to prevent restenosis after balloon angioplasty. However, one of the difficulties in using drug-eluting medical devices is finding ways to control the release rate of the drug.
In the past, the rate of drug elution from a coated medical device has been controlled by manipulating the coating of the device (see U.S. Pat. No. 6,274,294 to Hines et al., U.S. Patent Publication No. US2002/0050220 to Schueller et al., and U.S. Patent Publication No. US2004/0237282 to Hines et al.), or by manipulating the composition of the device itself (see U.S. Patent Publication No. US2005/0090888 to Hines et al.). However, these approaches are limited in their use, especially where a single medical device is needed to elute drugs at different rates, or where a single medical device needs to target drugs at a particular body tissue. While multiple materials could be used to make a medical device that releases drugs at multiple rates, this method is economically inefficient.
Accordingly, there is a need for a more efficient method of delivering a biologically active material to a targeted body tissue. There is also a need for a method that releases a biologically active material at different rates. Furthermore, there is a need for a method that releases a biologically active material from only a certain portion of a medical device. There is also a need for a medical device made by such methods.